Numerical and Experimental Analysis of the Flow in a Centrifugal

THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS 92-GT-284345 E. 47 St., New York. N.Y. 10017

The Society shall not be responsible for statements or opinions advanced in papers or in dis.cussion at meetings of the Society or of its Divisions or Sections, or printed in its publications.

M Discussion is printed only If the paper is published in an ASME Journal. Papers are available„L ® from ASME for fifteen months after the meeting.

Printed in USA.

Numerical and Experimental Analysis of the Flow in aCentrifugal Pump at Nominal and Partial Flow Rate

J. F. COMBESEDF/DER

Chatou, FranceE. RIEUTORD

INSALyon, France

Abstract

Detailed flow measurements in the impeller and thediffuser of an industrial centrifugal pump have been per-formed with a 2-component laser Doppler velocimeter.Measurements were made at 8 radial positions for flowrates ranging from 50% to 100% of design flow. The ex-perimental results were compared to 3D turbulent flow cal-culations performed with a finite element code. At nominalflow rate, both measurements and calculations show awake pattern along the suction side at the shroud. The flowis separated in the diffuser on the hub, and on the shroud atlow flow rate. The inlet recirculation, occurring at 0.65 Qnis well predicted by the turbulent flow calculation.

I- INTRODUCTION

Recirculations at the inlet and the outlet of centrifugalpump impellers are observed at partial flow rates, causingmechanical problems in pumping installations. In order tostudy these phenomena and to check the ability of numeri-cal methods to predict them, the Working Group 1-ef ofthe Soci6t6 Hydrotechnique de France (SHF) has carriedout a large research program since 1982. A centrifugalpump, representative of an industrial one, has been de-signed for this purpose. Two geometrically similar impel-lers have been manufactured and tested in different Euro-pean laboratories: a first one was tested in water at INSAin Lyon (France), EPF in Lausanne (Switzerland), andHYDROART in Milano (Italy); a second one (larger) wastested in air at ENSAM in Lille (France). The test con-

ditions (diffusers, volutes, ...) and the experimental tech-niques were different in each place: they are described byBarrand and al (1984 and 1985), Bois and Rieutord(1990), and Caignaert and al (1985 and 1989). The mainconclusions of these experiments were the following:

- the critical flow rate for the inlet recirculation hadthe same value (0.64 to 0.69 Qn) on every test rig, and forall the experimental techniques used to determine it: flow

105

Figure 1: Sketch of the SHF impeller. The full anddashed lines represent the 0-coordinate on both sides.

Presented at the International Gas Turbine and Aeroengine Congress and ExpositionCologne, Germany June 1-4, 1992

Copyright © 1992 by ASME

Downloaded From: https://proceedings.asmedigitalcollection.asme.org/ on 04/10/2018 Terms of Use: http://www.asme.org/about-asme/terms-of-use

298

346

451179 wmc784

Rn

749

)92

t82

vizualisation by threads, bubbles, cavitation, velocitymeasurements by 5-hole probe, fluctuating pressure meas-urements. This critical flow rate is also well predicted byFraser's criterion (1982).

- at the outlet, the critical flow rate is more dependenton the test conditions - air or water, rotation speed, diffusergeometry (vaned or unvaned, width), volute - and on theexperimental techniques. It varies from 0.63 to 0.84 Qn.

To evaluate the ability of numerical methods to pre-dict the flow in the impeller at nominal and partial flowrates, many companies and universities have run their owncodes (quasi-3D, Euler 3D (Combes, 1985), 3D boundarylayer (Ubaldi, 1985), secondary flows) and comparisonshave been made with the experimental results for differentflow rates. Some results were published by Philibert andVerry in 1985 and Ubaldi, Philibert and Verry in 1986.

The different inviscid analyses gave nearly the sameresults with a prediction of the outlet flow angle and inter-nal head very close to the experimental results for thenominal flow rate. Below 0.7 Qn, the internal head was un-derestimated, because of the outlet recirculation, whichwas not predicted at all. None of the inviscid analyses wasable to predict the inlet recirculation too. Using the invis-cid results, complementary information on the flow atnominal and partial flow rates was obtained from boundary

layer and secondary flow calculations. In the diffuser, theflow behaviour was well predicted using a model due toSenoo (1984), showing the separations on both sides, de-pending on the flow rate.

Since 1986, new computations were published: a me-ridional calculation for the turbulent flow was presentedby Martelli and Michelassi (1989) using a Baldwin-Lomaxmodel. Finally, a 3D k-c turbulent flow calculation at nom-inal flow rate was presented by Combes (1991), using a fi-nite element code. A critical review of the ability of thedifferent models, from 1D analysis to 3D fully turbulent,to predict the flow in a centrifugal pump is given by Bois(1992).

In this paper, we present the last experimental andnumerical results obtained for this test pump, i.e. a com-parison between LDV flow measurements at INSA andturbulent flow calculation with the finite element codeN3S, for different flow rates ranging from 0.6 Qn to Qn.

While laser velocimetry has become of commonpractice for the study of flow in turbomachinery compo-nents, only a few papers were published on measurementsin rotating parts in water, especially for shrouded radialimpellers. Adler and Levy (1979) measured the flow in ashrouded radial impeller with a single component LDVsystem. Kannemans (1980) performed measurements in a

Figure 2: Location of LDV measurement sections

Pa


shrouded fully transparent radial pump impeller. Grisonand al. (1984) compared quasi-3D calculations to LDVflow measurements for an industrial pump turbine model.Hamkins and Flack (1987) and Miner and al. (1989) meas-ured velocities within the impeller and volute of a 2D la-boratory centrifugal pump.

An extensive review of CFD techniques used for tur-bomachinery was given recently by Lakshminarayana(1991). Most of published turbulent flow calculations con-cern compressible flow in compressors or turbines. For in-compressible flow in pumps, one can mention the use ofpressure correction methods (Moore and al., 1990), orpseudo-compressible techniques (Goto, 1990).

II- DESCRIPTION OF THE SHF PUMP

The SHF impeller (figure 1) is a low specific speedcentrifugal impeller with 7 blades, an inlet diameter of 220mm, an outlet diameter of 400 mm, and an outlet blade an-gle of 22.5°. At 1200 rpm, the nominal flow rate is 0.1118

m3/s and the corresponding head 31 m. The design of theimpeller was made in order to make easier the experimentsand the calculations. Thus, in the radial part, the blades are2D and orthogonal to the hub and the shroud. However,the design is very close to an industrial one. Two modelswere built : the outlet diameters for the air and the watermodels are respectively 516.8 mm and 354.4 mm.

The water model was tested at INSA Lyon, EPF Lau-sanne and HYDROART Milan in different environments(diffuser, volute ...). For the measurements reported here-after, performed at INSA, the impeller was equipped witha six-blades diffuser whose leading edges are located rath-er far downstream of the diffuser inlet (figures 2 and 3).The volute is an industrial log spiral one with a quasi-cir-cular section (figure 2).

For comparison with the calculations, we also refer tothe velocity and pressure measurements performed in theunvaned diffuser of the air model by Maroufi (1986).

I

Figure 3: Optical arrangement for LDV measurements.


.8

3O=0n

(R/R2=.909 mid—channel).3

N 2 \

0 1 2 3 4 5 6 7

6M360'7 deg)

N i 4^^w y'''w,y.. .y,i^^•j, jAKy:•' C:. }^r•^. i..^t4':

u

4 L. Q=.6*On

(R/R2=.909 ; mid—channel)

.2

Ue

8 L 2 3 4 5 6 7

6 360/7Cdeg]

Figure 4; Typical circonferential distribution of velocity for two flow rates

III- FLOW MEASUREMENTS

An extensive mapping of the velocity field in theradial part of the impeller and in the diffuser has beenachieved using Laser Doppler Velocimetry (LDV).

Measurement domain

Figure 2 shows the position of the eigth measurementsections, three in the impeller and five in the diffuser. Ineach section, there was about fifteen measurement pointsthroughout the impeller or diffuser width.

All the measurements points are located in a samemeridian plane, diametrically opposite to the volute tongue

Li). V. measurements

The laser velocimeter used is a three beam Dopplersystem, with Bragg's cell frequency shift for measure-ments in reversing and highly turbulent flow. Using thegreen and blue lines of an argon-ion laser, this systemgives the radial Cr and tangential Cu absolute velocitycomponents. The use of a beam expander and a front lensof short focal length has allowed to obtain a very smallprobe volume, whose dimensions, defined by 1/e 2 intensi-ty boundary, are about 0.09 mm in the measuring direc-tions and 0.9 mm along the optical axis.

For these measurements, as shown in figure 3, a partof the impeller shroud has been replaced by a perspex an-nular window. Optical access to the measurement zone ismade through a window whose internal transparent partensures the continuity of the diffuser wall.

A 3D translation system allows the probe volume po-sitioning with a precision of 5 pm. The angular position,

with respect to the impeller is obtained using an opto-elec-tronic encoder with a resolution of about 0.09°(360°/4096).

Data processing

Two counter processors connected with a microcom-puter are used for signal processing and data acquisitionconcerning the Cr and Cu velocity components and the angular position of the impeller. The x, y, z coordinates,head, flow rate, torque and rotation speed are recorded si-multaneously.

For each measurement point, 2000 successive valuesof the instantaneous velocities and angular position are re-corded, in order to obtain, after statistical treatment, themean values used for comparison to theoretical data. Notethat, to increase the data acquisition rate, seeding particlesof Iriodine were injected in the flow, upstream the pumpinlet.

As an example, figure 4 shows, for two flow rates(Qn and 0.6 Qn) the instantaneous velocity components Crand Cu before any numerical treatment. The tick-marks onthe horizontal axis correspond to the blades position. Onthis figure, the blades are moving from right to left. At lowflow rate, it can be noted an important modification of thevelocity field with a significant increase of the fluctua-tions.

At nominal flow rate Qn , the standard deviation ofthe instantaneous velocity is about 0.01 U2 and can in-crease to 0.04 U2 when reducing the flowrate to 0.6 Qn.(U2 = wR2 , peripheral impeller speed)

4


the pressure. It is solved by a projected gradient UzawaIV- FLOW MODELIZATION

algorithm preconditioned in order to ensure a fast conver-

The N3S code gence.

In order to solve industrial flow problems in complexgeometries, a finite element code, N3S, has been devel-oped at Electricite de France. It allows the computation ofa wide variety of 2D or 3D unsteady incompressible flows,by solving the Reynolds-averaged Navier-Stokes equa-tions together with a k-e turbulence model. Some recentdevelopments of this code concern turbomachinery flows,where one has to take into account periodic boundary con-ditions, as well as Coriolis and centrifugal forces(Combes, 1991).

The space discretization uses a standard Galerkin fi-nite element method. In this calculation, the retained ele-ments are P1-isoP2 tetrahedrons verifying the LBB condi-tion.

The time discretization is based on a fractional stepmethod: at each time step, one has to solve successively:

- an advection step for the non-linear convectionterms of the Navier-Stokes and k and 8 equations. It istreated by a characteristics method.

- a diffusion step for the remaining part of the k and eequations: the finite element discretization leads to linearsystems solved by a preconditioned conjugate gradient al-gorithm.

- a generalized Stokes problem for the velocity and

The numerical method is described in details byChabard and al (1991).

Boundary conditions

The calculation was made for the nominal flow rate(Qn = 0.1118 m3/s), and for 0.8 Qn, 0.7 Qn and 0.6 Qn.The Reynolds number, based on the inlet velocity and theinlet diameter is about 650000 at Qn. It corresponds to aturbulent flow. For each flow rate, there was assumed noprerotation in the inlet section (Cu = 0), and that the veloc-ity profile corresponded to an established turbulent pipeflow. For off-design conditions, the same k and a distribu-tions than at Qn were used.

The boundary conditions used for the flow calcula-tion in the pump are the following:

- at the inlet, each variable, except the pressure, isprescribed. The calculation is performed in the relativeframe of reference, the tangential velocity component cor-responds to or.

- at the outlet, the normal stress was assumed to bezero, which corresponds approximately to a constant staticpressure. The gradients of k and a were also set to 0.

Figure 5: Finite element mesh

5


/ i///ir / iii

r r1

rt

1 1 1

icl•

- in order to avoid mesh refinements and the use of alow Reynolds turbulence model, wall functions were usedon fixed - inlet pipe, diffuser - and rotating walls - blades,hub and shroud.

- on lateral boundaries, assuming that the flow is thesame in each interblade channel, periodic boundary condi-tions were used for every variables.

Mesh

The computational domain corresponds to the impel-ler with an inlet pipe and followed by an unvaned diffuserup to a diameter of 500 mm (R/R2 = 1.25). By using peri-odic boundary conditions, the mesh corresponds to 1/7thof this domain.

The finite element mesh was built as follows:- H structured mesh (I-J-K) of the flow domain- triangulation of every I-surface with the same topol-

ogy, concentrating meshes around the leading and trailingedges

- constitution of a 3D mesh with prisms cut into tetra-hedrons

The global mesh (figure 5) consists in 28080elements and 43206 nodes. On the periodic boundaries,nodes and element faces correspond by rotation.

Calculation details

The whole calculation has been run in the followingway:

- mesh generation in prisms on a workstation- check and modification of the initial mesh (cut into

tetrahedrons, ...), boundary conditions setting- Flow calculation with N3S on the CRAY YMP.

The CPU time was about 10 hours for each flow rate andthe memory used 8 Mwords.

- post-processing on a workstation : calculation of Crand Cu from Cx and Cy for comparison with measure-ments

Other calculations

In the following we compare the turbulent flow cal-culations to results obtained with other codes in the Work-ing Group 1-ef of SHF. Among them, we performed an in-viscid calculation with a 3D Euler code (Caudiu and al,1988). This finite element code is based on a Clebsch-Hawthorne formulation. In the case of the SHF pump, thepotential version of this code was used on a mesh con-taining 3660 nodes and 675 isoparametric hexaedral ele-ments. The results obtained (Combes, 1985) are represen-tative of the other inviscid calculations for this pump.

V- RESULTS

The relative velocity and the pressure fields at nomi-nal flow rate are shown on a radial cross section next tothe shroud for two consecutive blade passages on figures 6and 7. The points on the periodicity boundary show the ra-dial positions where the calculation results are comparedwith the experiments. A first comparison at Qn betweenthe calculations and the flow measurements at INSA andENSAM was given by Combes (1991). The accordancebetween them was satisfactory : in the impeller, both cal-culations and measurements have shown a jet-wake flowpattern in the radial part. In the diffuser, a separation at the

Figure 6: Relative velocity field Figure 7 : Pressure field on a radial plane section

R


° R/R2=0.818

0.1 •^ ri*.^ • o o

0

0.15 °J R/R2 = 0.978 0

0.10 e• \Ô^°^"^

0. S.-

0.05.

OO o R R2 = 1.045

°/ 0'84° INSA \° 0.7Qn• Is0.6Q11I

0.0 0,2 0.4 0.6 0.81.0

mo _

d b/bmax ^b.

R/R2 = 0.818

•0.10] .

-

R/R2 = 0.978

oâ_^s- t •

'•r1_ •_____•_

-0.05 I . .0,0 0,2 0,4 0,6 0,8

1,0

shroud b/bmax

hk

Figure 8: Pitch-averaged radial velocity at 3 radial positions.

0.6 •8•_•_._ • 2=0.818•^ a•

❑^• ❑

0.5_I * * _a,_ ❑Ô`°^.^

0.0.4 p_ÔO0-0 OHO•0..

R/R2=0.978 . -•_••S..••••

0.6 • •JS.^:^❑^-'o-Ô^^❑ .❑

0.5

O.E R/R2 = 1.045

•^ o Qn0.4 ❑ r*0.7INSA

° 0.7J ..?' • 0.6 Qnna

0.0 0,2 0,4 0,8 0,8 1,0shroud b/bmax hub

0.6• RJR2=0.818 •rt• -•-• •-•0.5 O ❑ ,*^*.^❑^.°_te n 0^...❑ .❑A/O

•0.4. air CÔ^•p-0,•w•R/R2 = 0.978` 0.7

N %

V Oô0.5. 0.-_____

R/R2 = 1.045

0.7 • ./_• -•-• •_•-•--u

i

o.5 -

O On0.4 * 0.8 N3S❑ 0.7 On

• 0.6 Qn

0.3 1 I0,0 0.2 0.4 0.6 0.8 1.0shroud b/bmax byb

Fi r • Pitch-averaged tangential velocity at 3 radial positions.

7


O Qnac 0.8 Qn N3SO 0.7 Qn• 0.6 Qn

Shroud

U.

shroud •____0.15

n` U - •-•

0.10Q1+s^6y

O Qn

* 0.8Qn INSA0 0.7 Qn• 0.6 Q*i

0.2,5

0.20shroud

*__L\0.15 0^^5

077°Ô\

°^ ° •^•0.10lit •

0.05 ^^•^„^^•

0.so.00f 0.70n N3S

FO*.. 0.13 ;

0.6QnO^

o mid-

U 0.10 *y \channel oî

i ^^•♦

u.0 J • ^---r^

0.1

-

u^l 0.13VN

N40,

\ 0 O ` Y1S1]2

0.10 ^!

0.05

^„1000 j i- 0 O 0.2 0,4 O,8 0. 1,0

0,0 0,2 0,4 0,8 0,8 1,0suction pressure suction pressure

awa sins Aida Iida

Fi 1 • Radial velocity for 3 axial locations at the impeller exit (R/R2 = 0.978)

1.

0.90

.B 0.0.8

° 0.7 INSA[*0

0.v

• 0.6Qn

0.7 shroud 0.0

0.5 ^....,^^ ✓ ^

0.910.91

mid-channel0. *^°-^^`•^•o. o^^_ "-O ^.

0.9•

O _ "^ •tL

U- \pie * '

o.go. •N 0 7 • mid channel

C;

•0 .81\

0.7 •_ •

0.6• hk

0.5 O iF ^s ^^'M 0-O

0.4 ______o-° _

0__

00 0,2 0,4suctionside

O,s 0.8 1,0 0,0 0,2 0,4 0,6 0,8 1.0pressure suction oressuf6

Aida aaid& a

Figure1 • Tangential velocity for 3 axial locations at the impeller exit (R/R2 = 0.978)

8


hub was well predicted too.

Flow in the impeller

The measured and computed pitch-averaged absolutevelocity components Cr and Cu are plotted on figures 8and 9 for 3 radial positions and 4 flow rates from theshroud to the hub. In the impeller (R/R2 = 0.818), thecurves corresponding to the different flow rates are paral-lel. One can notice a higher radial velocity at the shroud.At the impeller exit, the slope of the radial velocity profilechanges with the flow rate: Cr begins to decrease at thehub, then at the shroud. In the diffuser (R/R2 =1.045), at0.6 Qn, the measured radial velocity becomes negative.The calculation exhibits the same behaviour, but less pro-nounced.

In the impeller, the measured and calculated tangen-tial velocities are nearly the same, but in the diffuser, atpartial flow rate, the calculation overestimates them. It re-sults an internal head Hi which is greater than the onemeasured by 2 to 5% while the internal head resultingfrom the inviscid calculations was about 5% lower thanthe experimental curve, except below 0.7 Qn where thediscrepancy was larger.

One can also notice the different behaviour of thetangential velocity profiles along the shroud and the hub,between the impeller and the diffuser. This effect corre-sponds to the different entrainment velocities : cur for theimpeller and 0 for the diffuser.

Figures 10 and 11 show the pitch-evolution of radialand tangential velocities at the impeller exit (R/R2 =0.978) at measuring points close to the shroud (b/bmax =0.05 to 0.1), at mid-channel (b/bmax = 0.5 to 0.52) andclose to the hub (b/bmax = 0.95 to 0.97). The inviscid cal-culation leads to a nearly 2D flow, with parallel evolutioncurves for the different flow rates, which looked like theone calculated using N3S at the hub or at mid -channel,except along the suction side. The evolution is also thesame at nominal flow rate for the measurements. At thehub, the measured radial velocity comes down to zero at0.6Qn.

The flow behaviour is quite different at the shrouddue to a wake located in the comer between the suctionside and the shroud. The N3S calculation gives a muchbetter flow modelization in this region. The relative veloc-ity is smaller and it corresponds to a high level of losses.When the flow rate is decreased, the flow becomes moreuniform in the impeller, but the measurements show an in-creased level of fluctuations.

There was no pressure measurement in the impeller,

so we can only compare the turbulent calculation to the in-viscid one. The pressure evolution curves have the sameshape except near the leading edge (see next paragraph)and at the exit, because of the losses. However, the pres-sure level at the diffuser inlet is very close to the measure-ments in air by Maroufi (1986). One can notice than theassumption of periodicity is not valid for the pressure, dueto the volute.

Inlet flow

At low flowrate, the SHF pump presents a recircula-tion zone at the shroud ahead of the blades. In the inletpipe, the core flow, with no prerotation, feeds the impeller,while an annulus of recirculating flow with a high rotationextends far upstream, depending on the flow rate. On eachtest rig, in water or in air, the experiments showed thesame behaviour with a critical flowrate of 0.64 to 0.69 Qn.For this critical flow rate, the flow presents large fluctua-tions, while for 0.6 Qn and less, the recirculation is stable.The recirculation was detected by means of visualizationby threads, cavitation or bubbles, and velocity and pres-sure measurements.

None of the inviscid flow calculations allowed theprediction of such a recirculation. A 3D boundary layeranalysis on the blade at 0.6 Qn did not show a separationat the leading edge which could be responsible for the re-circulation, but at about 25% of the chord length on thesuction side (Philibert and Verry, 1985). With the potential

11111 I//____ __,may////î

_-- -,.- _ --•iii/ / / /

__--------_. —` î/ice

Figure 12: Meridional velocity field at the inlet at 0.6 Qn

Z


calculation, the flow exhibits no prerotation ahead of theblades at any flow rate.

The turbulent flow simulation is quite different. Evenat nominal flow rate, the calculation shows a prerotationjust ahead of the leading edge, corresponding to the adap-tation of the flow to the blade. Due to this fact, thepressure distribution on the first part of the blades is differ-ent from the one resulting from the inviscid calculation.When the flow rate is decreased, this prerotation growsand extends upstream, especially at the shroud. At 0.7 Qn,with the exception of the hub region, it is noticeable up to1/3 radius before the leading edge, but no recirculation oc-curs; there is only a very short region of backflow alongthe leading edge.

On the contrary, at 0.6 Qn , a large recirculation zonewas observed (figure 12), quite similar to the one observedexperimentally. However, the upstream extension of thiszone is shorter than the one observed in air at ENSAM atthe same flow rate. This is due to the boundary conditionsat the inlet section located at about half a radius ahead ofthe leading edge, which block the recirculation zone devel-opment. On the blade, only the leading edge is affected bythis recirculation : on both sides, the flow reattachs imme-diately ; there seems to be no influence of the flow down-stream on the inlet recirculation.

Diffuser flow

The calculation of the flow with N3S corresponds tothe case where the impeller is followed by an unvaned dif-fuser, as it is not yet possible with this code to take intoaccount in the same calculation rotating and fixed parts.

INSAII II

sin 1 1 0.8 On 1 I 0.7 on I I I

So it was not possible to compare directly the velocity pro-files with the measurements at INSA where a 6-blades dif-fuser was used. At ENSAM, an unvaned diffuser wasused, but slightly wider than in the calculation.

The diffuser flow has been shown to be unstable, es-pecially at low flow rate, in the measurements and in thecalculation where the periodicity and the recirculationsperturb the flow development. A comparison at two radialpositions in the diffuser (R/R2 = 1.045 and R/R2 = 1.194)was presented by Combos (1991). The results were ingood agreement at the diffuser inlet, but at the exit, thetangential velocity was too high. In figure 13 we show thezones where the mean radial velocity becomes negative, atthe hub for Qn and at the shroud for 0.6 Qn. The same be-haviour was observed by Maroufi (1986) and also predict-ed by using a model due to Senoo (1984). In the impeller,the radial velocity becomes negative only at 0.6 Qn in thehub region (figurelO).

VI- CONCLUSION

New experimental and numerical investigations havebeen made on the SHF pump, designed for the study ofpartial flow rates in centrifugal pumps. The velocity fieldin the impeller and in the diffuser was measured by using atwo-component laser Doppler velocimeter from flow ratesranging from 50 % to 100% of the nominal flow rate. Theflow was also calculated using a finite element code. Therelative flow in the pump was assumed to be incompressi-ble, periodic, fully turbulent. The standard k-c model wasused, with wall functions suited to moving and fixed parts.

N3S

diffuser 1 I diffuscx 1 I diffuser

diffuser I I diffuser

-per- I I impeller I I —per- 11 impeller

I IIFigure 13: Recirculation zones in the diffuser.

impeller 1 1 impeller I I impeller I I impeller

iIE .0I I I

10


The velocity fields computed with N3S are in a goodagreement with the measurements, even in the zones af-fected by the viscous effects, where the inviscid calcula-tions fail to give good results. Thus, at nominal flow rate,the calculation, and the measurements, have shown phe-nomena such as wake flow at the shroud near the suctionside, recirculation at the diffuser outlet on the hub at nomi-nal flow rate and at the shroud at 0.6 Qn.

The turbulent flow calculation has also evidenced theinlet recirculation which occurs at a flow rate below 0.65Qn. The computed flow behaviour at 0.6 Qn is very similarto the one measured in the different institutions participat-ing to the SHF.

If confirmed by other calculations on different pumpgeometries, the ability of the numerical method to predictphenomena such as the inlet recirculation will be of greatinterest for the analysis of pump designs. Improvements inthe algorithm and the computing environment are in pro-cess in order to get an important reduction of the CPU timeand of the mesh generation and post-processing, and thenmake possible an industrial use of this kind of computa-tion.

References

ADLER, D., and LEVY, Y., 1979, "A Laser-DopplerInvestigation of the Flow Inside a Backswept, Closed,Centrifugal Impeller", Journal of Mechanical EngineeringScience, vol.21, pp. 1-6

BARRAND, J.P., CAIGNAERT, G., CANAVELIS,R., GUITON, P., 1984, "Experimental determination ofthe reverse flow onset in a centrifugal impeller", Proceed-ings of the 1st Int. Pump Symposium, Houston 'pp. 63-71

BARRAND, J.P., CAIGNAERT, G., GRAESER,J.E., RIEUTORD, E., 1985, "SynthBse de rdsultats d'essaisen air et en eau en vue de la detection des debits critiquesde recirculation h 1'entr6e et h la sortie de la roue d'unepompe centrifuge", La Houille Blanche n 3

BOIS, G., COMBES, J.F., RIEUTORD, E., 1992,"An analysis of flow characteristics of the rotor of an hy-draulic centrifugal pump using several CFD methods withdifferent levels of approximation", to be presented at IS-ROMAC 4, Honolulu

BOIS, G., RIEUTORD, E., 1990, "Etude de 1'dcoule-ment en sortie de roue de pompe centrifuge depuis le debitnominal jusqu'au debit critique de recirculation", Compterendu de fin d'etude de contrat MRT no 88H0636

CAIGNAERT, G., BARRAND, J.P., 1989, "Debitscritiques de recirculation: synthese de 1'ensemble des r6-sultats experimentaux sur les roues SHF essays es en air(ENSAM Lille) et en eau (INSA Lyon, EPF Lausanne,Hydroart Milan)", 20emes journees de 1'HydrauliqueSHF, Lyon, France.

CAIGNAERT, G., CANAVELIS, R., 1986, "Re-censement et examen critique des m6thodes exp6rimen-tales de detection des recirculations dans une pompe cen-trifuge", Symposium IAHR, Montreal, CANADA

CAIGNAERT, G., DESMET, B., MAROUFI, S. ,BARRAND, J.P., 1985, "Velocities and Pressure Meas-urements and Analysis at the Outlet of a Centrifugal Pumpimpeller", ASME paper 85-WA/FE-6, Miami Beach

CAUDIU, E., GRIMBERT, I., EL GHAllANI,E.M., VERRY, A., 1988, "3D Flow Calculations - Appli-cation to a mixed-flow pump and a Francis turbine", Sym-posium IAHR, Trondheim, Norway

CHABARD, J.P., METIVET, B., POT ,G., THO-MAS, B., 1991, "An efficient finite element method forthe computation of 3D turbulent incompressible flows", toappear in Finite Element in Fluids, vol.8.

COMBES, J.F., 1985, "Calcul de l'6coulement tridi-mensionnel potentiel Bans une roue de pompe centrifuge Adebit partiel", La Houille Blanche n 5

COMBES, J.F., 1991 "Application of a 3D viscousflow f.e.m. code to a centrifugal pump", 77th SymposiumAGARD - PEP : CFD Techniques for Propulsion Appli-cations, San Antonio ,Texas

COMBES, J.F., GRIMBERT, I., RIEUTORD, E.,1991, "An analysis of the viscous flow in a centrifugalpump with a finite element code", Fluid Machinery For-um, 1st ASME-JSME Fluids Engineering Conference,Portland,Oregon

FRASER, W.H., 1982, "Recirculation in centrifugalpumps", World Pumps, 1982-188 ,pp.227-235

GOTO, A., 1990, "Study of Internal Flows in aMixed-Flow Pump Impeller at arious Tip Clearances Us-ing 3D Viscous Flow Computations", ASME paper 90-GT-36

GRISON, P., VERRY, A., VILLARD, D., 1984,"Theoretical and Experimental Analysis of the 3D Flow ina Pump Turbine", Symposium IAHR, Stirling,UK

HAMKINS, C.P., and FLACK, R.D., 1987, "LaserVelocimeter Measurements in Shrouded and UnshroudedRadial Flow Pump Impellers", Journal of Turbomachin-

11


ery, vol.109, pp. 70-76

KANNEMANS, H., 1980, "Radial Pump ImpellerMeasurements Using a Laser Doppler Velocimeter",ASME paper 80-GT-94

LAKSHMINARAYANA, B., 1991, "An Assessmentof Computational Fluid Dynamic Techniques in the Analy-sis and Design of Turbomachinery - The 1990 FreemanScholar Lecture", Journal of Fluids Engineering,vol.113,pp.315-352

MAROUFI, S., 1986, "Contribution A 1'etude de 1'ap-parition des recirculations en sortie de roue dans unepompe centrifuge fonctionnant A debits partiels", These de3eme cycle, Universite de Lille

MARTELLI, F., MICHELASSI, V., 1989, "Pump de-sign by viscous calculations", 20eme journees de 1'Hy-draulique SHF, Lyon, France

MINER, S.M., BEAUDOIN, R.J., FLACK,R.D.,1989, " Laser Velocimeter Measurements in a Cen-trifugal Flow Pump", Journal of Turbomachinery,vol.111, pp. 205-212

MOORE, J., LE FUR, T., MOORE, J.U., 1990,"Computational Study of 3D Turbulent Air Flow in a Heli-cal Rocket Pump Inducer", AIAA paper 90-2123.

PHILIBERT, R., VERRY, A., 1985, "Flow calcula-tion in SHF impeller at 100% and 80% of design flowrate", La Houille Blanche n5

SCHIAVELLO, B.,SEN, M., 1980, "On the predic-tion of the reverse flow onset at the centrifugal pump in-let", 22nd Fluids Eng. Conf. ASME, New Orleans

SENOO, Y., 1984, "Vaneless diffusers", Von Kar-man Institute for Fluid Dynamics, LS 1984-07: Flow incentrifugal compressors

UBALDI, M., 1985, "Calcul de l'ecoulement vis-queux dans un canal de pompe centrifuge", La HouilleBlanche n5

UBALDI, M., PHILIBERT, R., VERRY, A., 1986,"Examen des possibilites et limites d'utilisation des calculsd'ecoulement pour la prevision des debits de recirculationd'une roue de pompe centrifuge", Symposium IAHR, Mon-treal, CANADA

12


Documents

Numerical and Experimental Analysis of the Flow in a Centrifugal